The European Central Bank is likely to refuse to show its hand on how it will help cut Greece's debt burden until investors and the government have agreed to a deal, said economists from ING Group to Deutsche Bank.

While Greece's creditors are increasing pressure on the ECB to join the bond swap being negotiated with the country, central bankers have remained silent on their intentions. Economists say the ECB wants to see the private-sector agreement concluded before indicating its strategy, which may include forgoing profits from its Greek bonds or a transfer to one of the region's rescue funds.

The Greek government needs to reach a deal and secure a second European Union-led bailout by March 20, when it faces a 14.5 billion-euro ($19.1 billion) bond payment. Charles Dallara, who as managing director of the Institute of International Finance leads a group negotiating on behalf of creditors, says involvement of public institutions is needed as bondholders hold only about 60 percent of Greek debt.